Details of the latest substantive reform to the Federal Fiscal Code.

On November 7, 2025, the Decree amending, adding, and repealing various provisions of the Federal Fiscal Code was published in the Official Gazette of the Federation, as part of the fiscal reform package aimed at strengthening Mexico’s tax collection and oversight system. Pursuant to the transitory articles, these amendments entered into force on January 1, 2026.

Several experts maintain that this is not an isolated technical adjustment, but rather a structural reconfiguration of the fiscal oversight paradigm. The reform expands verification tools, strengthens supervisory mechanisms, and provides the authority with more forceful instruments to detect non-compliance, simulation, and aggressive tax planning schemes.

However, this tightening is not novel in its essence. It represents the consolidation of a legislative trend that began years ago: the progressive strengthening of the powers of tax and customs authorities, the tightening of audit processes, the intensification of digital oversight, and the reduction of operational margins for taxpayers deemed to be high-risk.

One of the most significant changes, and the one that has generated the greatest concern among taxpayers, is found in Article 29-A, section IX, of the Federal Fiscal Code.

This provision introduces a substantive requirement for Digital Tax Receipts issued through the Internet (CFDI): formal compliance is no longer sufficient; the receipt must support existing, genuine transactions or real legal acts.

This requirement formalizes in the statutory text what had already operated in practice as an administrative criterion: the materiality and economic substance of transactions.

The substantial change introduced by the reform lies in the fact that the discussion previously focused on formal requirements and documentary compliance. However, as of January 1, 2026, it will no longer be sufficient to comply with formal requirements; it must also be proven that the transaction supported by the CFDI actually occurred in reality.

This could pose significant challenges for taxpayers, since for a CFDI to be considered valid, it is not enough to formally comply with all its requirements. To be valid, the materiality must also be proven. This is achieved by demonstrating that the transaction supported by the CFDI actually existed in economic reality, not merely on paper, whether through contracts, purchase orders, accepted quotations, infrastructure, hired personnel, assets, among others. Thus, materiality is evidenced through comprehensive, consistent, and traceable proof that demonstrates the economic reality of the transaction from legal, operational, and financial perspectives.

Likewise, the reform redefines the scope of the audit powers, and Article 42, section V, subsection g), expressly incorporates the authority to verify that Digital Tax Receipts issued via the Internet (CFDI) support real and not non-existent transactions.

With this amendment, the authority is no longer limited to reviewing the formal validity of the CFDI, but may also examine whether the underlying transaction actually occurred in material and economic terms.

Thus, a more demanding evidentiary standard is consolidated, as the taxpayer must not only prove the existence of a valid CFDI, but also that the transaction actually took place. In this context, the authority may analyze the following elements:

• The issuer’s actual operational capacity.
• Existence of assets, infrastructure, and personnel.
• Consistent and traceable financial flows.
• Consistent contractual documentation.
• Traceability of goods or services.
• Economic logic and reasonableness of the transaction.

On this regulatory basis, Article 49 Bis of the Federal Tax Code is structured to establish that when the tax authority, in the exercise of the power provided in Article 42, detects indications that the CFDIs do not support real transactions, it may initiate a special home inspection procedure with extraordinary characteristics.

This special procedure consists of an express audit, that is, an abbreviated audit process designed to detect simulated transactions within extremely short timeframes, with an approximate duration of 24 business days. In this process, the taxpayer has only 5 days to submit evidence of materiality before a possible final resolution.

The express audit procedure begins with notification, meaning that the SAT issues a visit order indicating the presumption of a false CFDI or that it supports non-existent transactions. Subsequently, the Digital Seals are suspended, that is, the taxpayer’s digital seals are immediately restricted, preventing them from issuing invoices. The taxpayer then has a period of 5 business days to refute the presumption and prove the materiality of the transactions. Documents demonstrating the real existence of the transaction must be submitted, such as contracts, emails, logs, photographs, bank statements, among others. Once the documents are provided, the authority must assess the evidence and issue a resolution within 19 days. If the irregularities are not disproved, the Digital Seal Certificate blockage becomes final and the taxpayer will be published on the blacklist under Article 69-B of the Federal Tax Code.

Thus, the 2026 reform consolidates a high-intensity audit model focused on economic substance and supported by expedited procedural mechanisms and precautionary measures that may be highly severe for the taxpayer.

The focus of tax control definitively shifts from formal compliance to the material verification of transactions. The debate no longer centers on the authority’s power to review materiality, which now has express legal support, but rather on the balance between collection efficiency and due process guarantees, since the mere presumption by the authority and its notification are sufficient to proceed with the cancellation of the Digital Seal Certificate, thereby completely halting the taxpayer’s operations, as without it issuing invoices becomes impossible.

The manner in which these powers are exercised and the standard of review adopted by the courts will determine whether we are facing an efficient audit model or a scheme that strains the constitutional limits of the Mexican State’s taxing power, given the tension between revenue collection efficiency and taxpayers’ rights.